Dr. Jeff Hersh: Tetanus uncommon but can't be eradicated

Q: Why do I need to get a tetanus shot; hasn't tetanus been eradicated in the U.S.?

Dr. Jeff Hersh

Q: Why do I need to get a tetanus shot; hasn't tetanus been eradicated in the U.S.?

A: Tetanus, sometimes called lockjaw because of the jaw muscle spasms that are often the first symptom of the disease, is a disorder of the nervous system caused by a toxin produced by the bacterium Clostridium tetani (C. tetani). The spores of C. tetani are found in soil worldwide, including in the U.S., where they can lay dormant for decades. When the spores are inoculated into a wound C. tetani may begin to grow; this is more likely if there is a co-infection from another type of bacteria, the wound has severe tissue damage from the injury or if the patient has certain conditions (such as diabetes) that predispose to infection. The C. tetani produce tetanus toxin which irreversibly binds to nerve terminals in the spinal cord and/or brain, causing the nerves to fire in an uncontrolled fashion. This entire sequence of events can take days or even months; hence the symptoms of tetanus may not manifest until days to months after the initial infected wound.

The symptoms of tetanus can be understood in terms of the uncontrolled nerve stimulation described above; the severity of symptoms depends on how much of the tetanus toxin is released.

Generalized tetanus is the most common form with symptoms of tonic contractions/spasms of the face/jaw, arms, legs, back, abdomen and/or neck as well as autonomic over-activity (irritability, restlessness, sweating and fast heartbeat which may progress to labile blood pressure and/or heart arrhythmias). The breathing and/or swallowing muscles may also be involved.

In rare cases the symptoms of tetanus may initially be limited to a localized group of muscles, although this almost always progresses to the generalized form. If the initial inoculation is via a wound to the head or neck then the nerves in the brain that control the eyes, face and/or tongue movements may be affected first; this often (but not always) evolves into generalized tetanus.

Tetanus in newborns is called neonatal tetanus, and most commonly manifests within a couple of weeks to a month after birth. In neonatal tetanus the spores typically enter through the area around the base of the umbilical cord, sometimes due to cultural practices where certain (possibly contaminated) substances are intentionally applied. Neonatal tetanus usually presents with muscle rigidity, inability to suck in order to feed and/or seizures.

Even though C. tetani is ubiquitous, tetanus can be prevented by adequate immunization. Because of this tetanus is very uncommon in the U.S. where vaccination is almost universal; however, about 40 cases per year still occur, usually in people with an incomplete vaccination history such as not having had a booster in the prior ten years. Studies have shown that up to a third of Americans over age 70 do not have adequate antibody levels.

Neonatal tetanus is rare in the U.S. due to protection from mom's antibodies (from maternal vaccination) shared in utero. The baby will subsequently develop their own immunity from the full series of vaccinations given at ages 2, 4, 6 and 15-18 months, at then at 4-6 years of age with subsequent boosters every 10 years (or 5 years when there has been a concerning wound).

In developing countries where many people are not immunized, tetanus is unfortunately very common. There are over a million cases of tetanus worldwide every year, resulting in up to 500,000 deaths. Neonatal tetanus is also common, killing up to 60,000 newborns worldwide every year.

There is no cure for tetanus. Treatment is focused on minimizing how much toxin is released into the system by appropriate wound management (debriding dead tissue to eradicate spores), antibiotics to kill the C. tetani (although this is at most a minimal benefit), and immunization to minimize the effect of any unbound toxin. Because the effects of the toxin on the nerve terminal are irreversible, supportive care of the patient (including muscle relaxants, respiratory support and even induced paralysis and other care) is needed until the nerve terminals can regenerate (about 4-6 weeks) allowing symptoms to resolve.

Prognosis depends on the amount of toxin released and the extent of disease from it. Severe cases have widespread muscle spasms from extensive nerve involvement and without treatment the majority of these patients die; even with supportive care over 10 percent still die.

Tetanus cannot be eradicated, but it is very uncommon in the U.S. due to our effective vaccination program. Don't become a statistic; be sure your tetanus shot is up to date!